title: Homophilic binding properties of galectin-3: involvement of the carbohydrate recognition domain.
abstract: Galectin-3, an animal lectin specific for beta-galactosides, is composed of three different domains. The N-terminal half of the molecule (N domain) consists of a short N-terminal segment followed by glycine-, proline-, and tyrosine-rich tandem repeats. The C-terminal domain (C domain) harbors the carbohydrate recognition domain homologous to other members of the galectin family of lectins. Galectin-3 aggregates in solution, and participation of the N domain of the molecule in this process has already been demonstrated. Using a solid-phase radioligand binding assay, which allows the direct analysis of galectin-3 self-association, here we provide evidence that the carbohydrate recognition domain of the lectin is involved in carbohydrate-dependent homophilic interactions: (a) Radiolabeled galectin-3 binds to immobilized galectin-3, and the addition of unlabeled galectin-3 in solution increases the rate of binding of radiolabeled lectin; (b) binding of radiolabeled galectin-3 to immobilized galectin-3 is inhibited by the C domain; (c) binding of radiolabeled galectin-3 to immobilized galectin-3 or the C domain is inhibited by lactose but not by sucrose; and (d) the radiolabeled C domain does not bind to immobilized C domain. Taken together, these data suggest that in addition to the N domain, the homophilic interactions of galectin-3 are mediated by the C domain.
authors.affiliation: Department of Biochemistry, Institute for Animal Anatomy and Physiology, University of Bonn, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Kuklinski
authors.forename: R
authors.initials: R
authors.lastname: Probstmeier
mesh_terms: D000943:Antigens, Differentiation / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D001665:Binding Sites; D037502:Galectin 3; D005998:Glycine; D007457:Iodine Radioisotopes; D007700:Kinetics; D007797:Laminin / Q000378:metabolism; D037102:Lectins / Q000737:chemistry / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000378:metabolism; D011392:Proline; D011869:Radioligand Assay; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D014443:Tyrosine
chemical_list: D000943:Antigens, Differentiation; D037502:Galectin 3; D007457:Iodine Radioisotopes; D007797:Laminin; D037102:Lectins; D008562:Membrane Glycoproteins; D011994:Recombinant Proteins; D014443:Tyrosine; D011392:Proline; D005998:Glycine